As-built map accuracy and timeliness were Questar Gas’s primary
concerns. The company’s pipeline inspectors traditionally collected
gas mains and services as they were installed by contractors. Prior to
the GPS-based solution, inspectors used measuring tape and paper to
record the diameter and length of the pipes put in the ground. The tape
was used to locate the pipe offsets relative to nearby physical features
such as building foundations, fences and sidewalks. This information
was hand-sketched on paper in the field.

“We would station the main and then measure offsets every 100
feet as tie points to physical features,” said Zesiger.

Next, the inspector returned to the service truck to access
a computer and digitally re-draw the paper sketch into a simple
mapping application. The data was later uploaded back to Questar
Gas’s engineering department. There, GIS specialists recreated each
service map with associated attributes into the enterprise GIS.

“It took an inspector 25-30 minutes to map each service install
with the two-step process in the field,” said Zesiger, pointing out that
it required more scheduling of inspectors to ensure correct installation
practices. Under the best of circumstances, the accuracy of these maps
was about one foot, but problems arose when the features used as tie
points were altered. Moved fences and widened roadways introduced
errors in the mapped locations of main and service pipes.

The other problem was timeliness, Zesiger explained, “During
the busy construction season, replacements and large projects could
take up to two months for the as-built information to get into the GIS.”
Until the data was officially added to the GIS several weeks later,
Questar Gas was unable to provide line location information to other
utilities working in the area or even residents planting trees around
their new houses. Lack of timely as-built data in a widely accessible
database contributed to tear outs, which are expensive and dangerous
problems for everyone.

GPS As-built Mapping

The Questar Gas GPS as-built mapping system is developed on
the CartoPac Technology Platform. After evaluating several mobile
hardware options, the utility opted to standardize on integrated GPS
data collection equipment from Trimble Navigation, currently the
Trimble Geo Explorer 6000 and Geo 7X handhelds. Each is linked
to an external antenna for higher accuracy GPS signal acquisition
around buildings, and a laser range finder for measuring distances in
difficult-to-access places.

“During the implementation of the system we decided tocoincide its rollout with initiation of company-wide standards for datacollection,” said Zesiger. “We bring our inspectors in for a week oftraining and education on our efforts to standardize asset inventoriesacross the organization to ensure everyone maps assets in the exactsame way.”A typical gas service installation occurs in a subdivision thatis still under construction and begins with a call to Questar Gas’pre-construction representative from the general contractor. Apreconstruction representative enters the details into a custom-builtwork order management system called the HUB where it is routed toengineering for initial design approval. Utility engineers determinethe size and location of gas mains and services that will run throughthe new neighborhoods and to individual houses. Technicians enterthe mains and services into the GIS as proposed lines so that they arevisible prior to and during construction. They design redlines in ESRIArcGIS software.

“The installation contractors and our inspectors are assignedto zones within our service territory,” said Zesiger. “Once redlinesare completed, the work order management system releases theinformation to the appropriate contractors and inspectors.”Using the proposed redline as a guide, the contractor’s job is toinstall gas mains in the new subdivisions and then run service linesin the property to the service hookup on the side of the house. Thecontractors are paid based on linear feet of installed pipe trencheswith additional pay for cutting asphalt, directional drilling and otherspecial circumstances.

At each job site, the inspector uses the touchscreen on a Trimble
data collector to enter a project number for the installation into the
GPS as-built mapping software. Once the pipe is laid in the ground,
the inspector climbs into the trench with the GPS data collector to
map the location of the pipe.

“The Trimble device communicates with the Utah VirtualReference Station (VRS) network, which provides real-time GPScorrection,” said Zesiger. “This gives them an accuracy of plus orminus four inches, and the software lets the inspector know he’sgetting the configured accuracy for location data as he walks.”“The inspector just scans the barcode on each feature, and thesoftware populates the attribute table with 16 details contained inthe bar code about it, including composition and manufacturer,” saidVlass. “This eliminates time-consuming data entry by the inspector.”For the average new home service install, the Questar inspectortakes about 10 minutes to map the service, connection with the main,scan barcodes and collect relevant photos. The software in the deviceuses the sub-foot GPS points to create a very accurate map of the